In a conventional manner, an alternator fitted to a motor vehicle comprises a stator in which is placed a rotor, a shaft of which is rotationally driven by the vehicle's internal combustion engine by means of an appropriate device. In a manner which is also conventional, the stator comprises at least two armature windings connected to a rectification device to form two power supply sources.
As a result of the method of driving the rotor, the performance of such an alternator varies with the speed of the internal combustion engine. However, the vehicle's own systems need a power supply of constant voltage.
In order to remedy this drawback, it is known, in particular, for two independent three-phase windings to be made at the stator and for an electronic circuit to be added, connecting the said windings, making it possible, depending on the speed of the vehicle's internal combustion engine, to connect the said windings in series or in parallel. More precisely, the said connecting electronic circuit makes a series connection of the said windings when the engine speed is low in order to obtain a high off-load voltage and high current at low speed at the alternator output and a parallel connection in the case of high speed of the said internal combustion engine, in order to increase the current delivered by the said alternator.
In a known manner, each of the three-phase windings is associated with a diode rectification device and several solutions are known in the prior art for making the above-mentioned connecting electronic circuit. For example, document FR2807232 proposes associating each of the diode rectification devices of the two three-phase windings with an auxiliary bridge rectifier also made up of diodes and connecting the said auxiliary bridge rectifiers by switchable means such as, but without being restricted to, a transistor, controlled diode or a switch. Document U.S. Pat. No. 6,005,786, for its part, proposes placing the following directly at the outputs of the two three-phase windings, each associated with its rectification device: a set of switchable means with which it is possible to interconnect some of the outputs of the said windings, depending on the number and nature of the switchable means activated.
Even if, with these coupling modes, it is possible to obtain satisfactory alternator performance, the said coupling modes nevertheless involve the use of a relatively large number of electronic components, which increases the alternator's overall dimension. As, on a motor vehicle, the alternator is located in a restricted space, the constraints linked with its overall dimension also involve the said electronic components' being relatively close to one another. As a result, it is then necessary to add a set of means with which the thermal dissipation of the calories emitted during operation can take place (fans, liquid circulation cooling devices, etc.), which increases the complexity of the alternator and therefore its cost.
The aim of this invention is to propose a rectification device for an alternator intended for a motor vehicle, in which the number of electronic components is small, whereby the overall dimension of the said alternator can be reduced, while high performance is retained in terms of voltage and current delivered, irrespective of the speed of the vehicle's internal combustion engine.
With this aim, the principal object of this invention is a power supply device, particularly for a motor vehicle's own system, that comprises a set of armature coils assembled in a polygonal coupling mode, i.e. connected to one another in hexagonal coupling so as to form a polygon. Moreover, the armature coils are connected to a single bridge rectifier comprising a set of controllable elements with which switching can be carried out between a first operating mode in which some of the armature coils are electrically connected in series, and a second operating mode in which all of the armature coils are electrically connected in parallel.